* @throws NullPointerException if any element of {@code keys} is {@code null}, or if {@code
   *     valueFunction} produces {@code null} for any key
   * @since 14.0
   */
  public static <K, V> ImmutableMap<K, V> toMap(
      Iterable<K> keys, Function<? super K, V> valueFunction) {
    return toMap(keys.iterator(), valueFunction);
  }

  /**